Saltar la navegación

9.3.2. Reptiles

Class Reptiles

Reptiles are terrestrial vertebrates (the majority, there are also some aquatictetrapods that evolved from amphibians about 270 my ago In the Mesozoic Era they dominated all environments, but many became extinct, like the dinosaurs, when the Era ended.

They are tetrapods, so most reptiles, such as lizards and tortoises, have four legs. These legs are usually short and end in five toes with nails. Other reptiles, such as snakesare limbless, although because of their evolutionary parentage they continue to be classified as tetrapods.

Reptiles are ectotherms, so they cannot regulate their temperature. They tend to live in warm places and are lethargic when it is cold.

When reptiles grow, they have to molt, shedding old skin. Snakes often lose all of their skin.

Evolution has led them to have a series of adaptations that have allowed them to become independent of water.

They have pulmonary respiration. Their lungs are more complex than those of amphibians, so they take in more oxygen and do not need skin respiration. That is why they have been able to cover their body with horny scales that waterproof them against desiccation. In some cases, such as in turtles, the scales join together to form a very hard shell.

The sense organs are grouped mainly in the head. Most of the receptors for taste, smell, and touch are concentrated on the tongue.

The reptilian heart consists of two atria and one ventricle, which is partially septate in more evolved reptiles.

Most reptiles are carnivorous, killing their prey with their teeth. Some kill their prey by suffocation or by injecting it with poison before swallowing it. Some turtles, lizards, and iguanas are herbivores.

Its reproduction is sexual, with internal fertilization. Sometimes copulation is preceded by courtship.

Most are oviparous. Their eggs have amnion and a shell that prevents desiccation during embryonic development, which takes place on land. Others, like the viper, are ovoviviparous, and the eggs hatch inside the body of the female.

Types of reptiles

If we want to review the main types of reptiles, we have to remember the great reptiles, such as the dinosaurs, which inhabited the Earth during the Mesozoic, but which, however, are all extinct and we can only find their fossils.

The main groups of current reptiles are:

  • Order Squamata (scaly).
  • Order Chelonians (turtles).
  • Order Crocodylia (crocodilians).

Tipos de reptiles

Order Squamata (scaly)

The scaly are reptiles that are characterized by:

  • Your skin, covered by corneal scales, have to move it several times throughout your life.
  • His tongue is bifida.

The scalyes are divided into two groups :


  • Reptiles such as lizards, geckos, iguanas, chameleons, and geckos are included in the lizards.
  • Most saurians are terrestrial, but there are also  arboric, excavators and water species.
  • They are carnivores, good hunters, and they feed mainly on insects.
  • All its legs have five fingers.
  • His eyelids are mobile.
  • Many saurians, if they are in a situation of danger, can detach their tail in order to escape and later, it will regenerate. All the Saurians of Spain, except the chameleon, can lose the tail. The chameleon, on the other hand, can change its color as a defense method or by other environmental reasons.



  • In offerings include snakessnakes and vipers.
  • Although they are usually terrestrial, there are also aquatic species.
  • Their body is very elongated and they lack limbs. They use the muscles of their body to move through undulating movements.
  • They molt during their growth.
  • They are carnivores. Their diet is based on small mammalslizardsamphibiansfish and insects. They are adapted to this feeding, some with a mouth that can be greatly dilated because the jaws are joined by ligaments, others with poisonous glands with which they inject poison into their prey, others suffocate their prey, etc.
  • The bite of some snakes is poisonous.
  • They have no eyelids. They protect their eyes with a transparent membrane that allows them to see. Their vision is not especially good, nor do they need it, since they are at ground level. Some species, such as vipers, have organs that allow them to detect heat.

Culebra bastarda (Malpolon monspessulanus)

Culebra bastarda (Malpolon monspessulanus) en Rodanas, (Épila ,Zaragoza)

Game: Which snake from the Iberian Peninsula are you?.

Curiosity: the flying snakes

Can snakes fly?

Well, fly like a bird, no. But the flying snake (Chrisopelea) can glide up to 100 meters in the air. Its body adopts a flat shape by opening its ribs, making its body wider and facilitating gliding.

Do you want to see how these snakes fly?

Order Chelonians

  • Chelonians (tortoises and freshwater turtles) are reptiles that do not have teeth. Their jaws are shaped like a sharp beak with which they cut food.
  • They have a bony shell covered with horny plates that covers the trunk, and in which they can hide their head and limbs. Marine species cannot hide their head and limbs inside the shell. The shell has two distinct parts:
    • Back: on the dorsal part, it is the most convex area.
    • Plastron: on the ventral part, it is the flat area.
  • Food varies according to its habitat. Terrestrial turtles are usually herbivorous, while aquatic turtles are carnivorous, feeding on amphibians, fish, carrion, etc.

El caparazón forma parte del esqueleto de una tortuga

Cmglee [CC BY-SA 3.0 or GFDL], from Wikimedia Commons

Are all turtles slow?

Whenever we think of a turtle we imagine a slow, very slow, extremely slow living being that can hardly drag its shell.

Do you want to see how fast an Apalone spinifera or spiny softshell turtle moves?

Order Crocodylia

  • The reptiles of the crocodilian group (crocodiles, alligators and gharials) are great hunters.
  • They are large.
  • They are protected by bony plates (osteoderms) that act like armor.
  • They are carnivores. Their jaws are very powerful (crocodiles and alligators) and their teeth are very strong.
  • They have adaptations to the aquatic environment, such as the laterally compressed tail to facilitate movement in the waternictitating membranes in the eyes, webbed fingers, etc.
  • We can identify the different groups of crocodilians by:
    • Crocodiles: Their body is narrow and the head is elongated.

Cocodrilus acutus (cocodrilo americano)

By Petruss [CC BY-SA 3.0 ], from Wikimedia Commons

  • Alligators: Their bodies and heads are wide.

Caimán del Misisipi o aligátor americanoBy PetarM [CC BY-SA 3.0 ], from Wikimedia Commons

  • Gharials: Its long and thin snout stands out. It has many teeth but very small.

Gavial - Gavialis gangeticus (Gavial del Ganges)

By Cliff [CC BY 2.0 ], via Wikimedia Commons

Another reptile, the tuatara

The tuatara (or sphenodont) is a reptile that does not belong to any of the groups in which we have classified reptiles. It is a very primitive reptile, quite similar to iguanas that only lives on the islands near New Zealand.


Comparison between scaly reptiles (saurians and ophidians), chelonians and crocodilians

Differences between Squamates (saurians and ophidians), Chelonians and Crocodilians
Order Squamata (scaly) Order Chelonidae Order Crocodylia
Skin covered by horny scales Bony shell covered with horny plates Protected by bony scales, like armor
forked tongue They do not have teeth, but their jaws are beak-shaped with which they can cut food. Very powerful jaws with very strong teeth
They shed their skin

Saurians: many can lose their tails to try to distract their predator, which will regenerate later

Ophidians: elongated body, no limbs

Saurians (lizards, lizards). Ophidians (snakes) Turtles and Galapagos Crocodiles, alligators and gharials